Lexical stress is an important component of pronunciation in many languages. For instance, in the English language, native speakers rely not only on the pronunciation of sounds, but also on the stress patterns, to understand spoken words; use of an incorrect stress pattern can greatly reduce a speaker's intelligibility. This presents a challenge for individuals learning new languages, particularly when those individuals' native languages use more consistent lexical stress patterns or incorporate timing and rhythm in different ways.
Conventional language learning applications that attempt to classify lexical stress usually do so at the word level (i.e., simply indicating which syllable of a word was the most stressed). That is, such systems assume that exactly one syllable in every word has primary stress. However, an individual learning a new language may in fact stress more than one syllable in a given word; thus, this conventional approach is not always appropriate or effective.
Moreover, many conventional language learning systems require that a word be pronounced correctly phonetically before making a decision about stress level. Since phonetic and stress pronunciations are often tied together, however, such systems may miss numerous opportunities to correct stress pronunciation mistakes.